Electric induction apparatus



Dec. 21, 1943. J PETERSQN ELECTRIC INDUCTION APPARATUS Filed Feb. 11..1942

Inventor:

r Imm efit P A E H Tmy b Patented Dec. 21, 1943 ELECTRIC INDUCTIONAPPARATUS Justin Peterson, Swampscott, Mass., assignor to GeneralElectric Company, a corporation of New York Application February 11,1942, Serial No. 430,408

6 Claims.

This invention relates to induction electric apparatus and to movablecoil constant current transformers and reactors. Constant currentelectrical apparatus of this type consists of relatively movablewindings and a core providing a magnetic circuit inductively relatingthe windings, the magnetic repulsion between the windings being a factorin determining the relative positions of the windings at any instant,and hence the current supplied to the load.

In order that the movable windings may respond accurately to changes incurrent, provision is usuall made to prevent the movable windings frombinding against the core legs, and it is a practice to provide a guidingmeans for the movable winding in the form of an arm pivoted at its outerend to an extension of the core clamping structure. Furthermore, themovable winding of the conventional transformer is of such a weight thata counterbalancing means is required for at least partially neutralizingthe effect of gravity thereupon. The counterbalancing mechanism in itssimplest form usually consists of a fulcrum lever mounted upon the uppeend of the magnetic core structure and which is connected to one end bymeans of a pivot link to the movable coil on the side opposite thepivoted guide I arm. Suitably arranged upon the fulcrumed lever is anadjustable Weight by means of which the regulation of the transformermay be adjusted. The regulation of such a simple counterbalancedtransformer is relatively poor, usually varying within plus or minusseveral percent, which in the case of'a lighting load results inabnormally short lamp life. To improve the regulation of the transformerspecial precautionary measures must be taken, usually in the form of arelatively complex linkage mechanism between the counterbalancing weightand the'movable coil, which includes numerous ball bearings andcarefully machined parts together with precision adjusting means. In theevent that such a transformer is to be arranged within an insulatingliquid filled tank such as may be required for pole mounting, the tanksize required is relatively large. The larger the tank, the greater thequantity of insulating liquid required,- and the more difilcult becomesthe mounting problem so that it isex tremely desirable to reduce theoverall dimensions of such transformers to a minimum.

It is, therefore, an object of the present invention to provide a newand improved electrical apparatus of the movable coil type whichrequires no mounting brackets for the movable coil nor anycounterbalancing weight and associated lever mechanism. 1 l

It is a further object of the present invention to provide a new andimproved constant current electrical apparatus of the movable coiltypein which the movable coil floats substantially rectilinearly withrespect to the stationary coil without the need for any lever orcounterweight mechanism to efiect partial compensation for the force ofgravity acting upon the movable coil.

It is another object of the present invention to provide a new andimproved regulating device of the movable coil constant current type inwhich the movable coil is specially constructed so that the force ofmagnetic repulsion is greater than For a consideration of what I believeto be novel' and my invention, attention is directed to the followingdescription and the claims appended thereto taken in connection with theaccompanying drawing.

In the drawing Fig. 1 is a side elevation of a constant currenttransformer constructed in accordance with one form of the invention;Fig.2

d is a set of curves illustrating regulation characteristics which willbe employed in describing my invention, and Fig. 3 diagrammaticallyillustrates a constant current electric apparatus which is provided withmy improved current regulating arrangement. I

Referring to the drawing, the constant current transformer comprises amagnetic core structure having a winding leg l0 and a pair of outer legsH which cooperate to define a pair of windows within which are arrangedthe primary and secondary winding coils I2 and I3 surrounding thewinding leg in. The primary winding l 2 is fixedly arranged in the lowerend of the window while the secondary winding 43 is movably arrangedthereabove for substantially rectilinear movement in the verticaldirection parallel with the sides of the winding leg In. It is, ofcourse, to be 1 formers in which the secondary winding is supported upona hinged bracket arm, the opening through the center of the winding coilmay be round instead of oblong as is required in the case of thepivotally supported windings. Thus a saving in the overall dimensions ofthe transformer is effected.

In the usual constant current transformer the force of gravity actingupon the moving coil is considerably greater than the force of repulsionresulting from the currents flowing through the two windings. This istrue even in the case of transformers immersed in oil in which instancethe buoyancy effect of the oil upon the movable winding is appreciable.This latter effect, however, is still not sufficient to eliminate thenecessity for a counterweight and balancing lever even in the case ofmachines having a 50 per cent reactance and with a cross section ofcopper adequate to obtain satisfactory cooling with noncirculating oil.

In the case of the present invention the moving coil is so designed andhas such mechanical and electrical characteristics that the force ofrepulsion plus the buoyancy of the oil is greater than the weight of themovable coil assembly. For this purpose the movable coil may be wound ofany suitable material, such as aluminum wire or, should it be desired touse copper wire, suitable floats (not shown) may be attached to theupper surface of the movable coil. In the case of the aluminum Woundcoil, notwithstanding the fact that a greater cross section of conductoris required over that in the case of a copper conductor due to the lessfavorable conductivity of aluminum, the force of repulsion plus thebuoyancy of the fluid is amply sufiicient to overcome the force ofgravity.

In order to assure that the secondary winding will not bind against thesides of the winding leg or the adjacent faces of the outer leg and willbe maintained in a spaced relation therefrom, suitable means may beprovided for guiding the movement of the coil between its upper andlower limits of travel. A pair of guide rods M are provided, one on eachof the opposite sides of the assembly, one being shown in Fig. 1, whichguide" rods are secured at their upper and lower ends to bracket arms l5and [6 extending outwardly from the upper and lower portions of the corestructure, respectively. The secondary winding is clamped betweensuitable upper and lower clamping members IT and I8, respectively,through bolts l9. Rollers 2i) and 2| suitably secured to the upper andlower coil clamps H and i8, respectively, are adapted to engage with theguide rods M to maintain the secondary coil 13 properly spaced withinthe core window. The rollers and 2| are provided with grooved faces forcooperatively fitting around the vertical guide rods and thusdetermining the path of movement for the coil. It is to be understood,however, that the movable coil may be allowed to move without guiderollers so that it may wobbl slightly,

and still a substantially rectilinear movement will obtain.

A transformer constructed as described above has a regulationcharacteristic as is indicated by the curve of Fig. 2. It will be seenthat this characteristic is very fiat up to about onehalf load, and itdroops slightly from there to full load. This drooping may be due to aproximity effect when the coils approach each other as it has beenobserved that as the coils approach each other the force of repulsiontends to increase for a given current.

In case a characteristic is desired which is even flatter than that ofcurve 30 of Fig. 2, this variation in the repulsive force between thetwo coils may be counteracted by a compensating means which includes anelectromagnetic arrangement having a solenoid winding 3| which ismounted upon the upper end of the magnetic core structure and connectedin series with the secondary winding I3 through conductors 32, 33, 34,and a suitable load such as lamps 35, as will be seen in Fig. 3. Thecompensator solenoid winding is hollow and is vertically arranged,preferably coaxially with the primary and secondary windings, and issuitably anchored to the upper core clamping structure. A solenoid corecomprising a central leg 36 and a pair of outer legs 31 connectedtogether by an upper yoke portion is supported above the solenoid bymeans of a suitable yoke bracket 38, the legs of which straddle theupper yoke of the transformer core structure and the lower ends of whichlegs being secured to the upper clamping member I"! of the secondarycoil by a bolt 46. The central leg 36 of the solenoid core issubstantially centrally aligned with the opening in the solenoid coil 3!so that it may move freely in and out without frictional engagementtherewith as the secondary winding moves.

Since the solenoid coil 31 is connected in series with the secondarycircuit and will have substaniially constant current flowingtherethrough, the magnetic flux on the solenoid core will increase asthe core is inserted deeper into the coil. In this manner the movablecoil will be biased towards the stationary coil by a force which is afunction of or inversely proportional to the spacing between thewindings. Thus, the increasing pull of the solenoid offsets theincreasing repulsion as the moving coil approaches the stationary coil,and the secondary current may be held practically constant, as isillustrated by curve 40 of Fig. 3.

To adjust the particular value of secondary current which is to be heldconstant by the device, an adjustable weight M consisting of a pluralityof shims may be provided such as upon a bolt 42 extending from the upperportion of the solenoid core supporting bracket 38. Also the regulationof the transformer may be varied by providing a movable tap 43 for thesolenoid coil 3| which will vary the range of the force due to thesolenoid.

Thus, it will be seen that a transformer constructed as described aboveis relatively compact in design and comprises relatively few movingparts, and is characterized by a complete absence of pivoted levers,connecting linkages and the like. By the elimination of such levers andlinkages, the overall dimensions are practically reduced to thedimensions of the core and coil units so that a reduction may be made inthe size of the tank or enclosure provided for closing the device.Corresponding savings in the amount of oil and overall weight of theunit are effected and which lessen the problem of mounting such a deviceon poles.

Although I have shown and described particu lar embodiments of myinvention, I do not desire to be limited to the particular embodimentsdescribed, and I intend in the appended claims to cover allmodifications which do not depart from the spirit and scope of myinvention.

What I claim as new and desire to secure by Letters Patent 01 the UnitedStates is:

1. In a constant, current electrical apparatus, the combination of amagnetic core having a winding leg, of a plurality of windingssurrounding said leg, one of said windings being adapted to movelongitudinally along said leg in response to reaction between thecurrents flowing through said windings, and electromagnetic means forexerting a biasing force against said movable winding, said biasingforce being a function of the spacing between said windings.

2. In a constant current transformer, the combination with a magneticcore having a substantially rectilinear winding leg and cooperatingmembers forming a window, of a plurality of windings surrounding saidleg, one of said windings being adapted to move substantiallylongitudinally of said leg in response to reaction between the currentsflowing through said windings, and electromagnetic means exerting aforce against said winding tending to prevent movebiasing force againstsaid movable winding tending to prevent separation of said windings,said biasing force being greater in accordance with the proximity ofsaid windings relative to each other, said biasing force being of suchmagnitude as to effect a substantially constant current regulation forsaid transformer.

-4. In a constant current transformer, the combination with a magneticcore having asubstantially rectilinear winding leg and cooperatingmembers forming a window, a primary winding surrounding said windingleg, a secondary winding surrounding said leg above said primarywinding'and adapted to move relative to said primary winding in responseto reaction between the currents fiowing through said wind- 1 85. asolenoid supported on said magnetic core and connected in series withsaid secondary winding, and a magnetic core movable with said secondarywinding and having a portion magnetically associated with said solenoid,a coupling between said core and said solenoid varying in accordancewith, the spacing between said windings,

5. In a constant current transformer, the combination with a magneticcore having a substantially rectilinear winding leg disposed in asubstantially vertical position and cooperating members forming awindow, a primary winding surrounding said winding leg, a secondarywinding surrounding said leg above said primary winding and adapted tomove relative to said primary winding in response to reaction betweenthe currents flowing through said windings, means secured to saidmagnetic core for guiding the movement of said secondary winding in avertical direction substantially parallel with and in a spaced relationwith respect to said winding leg, a solenoid supported on said magneticcore and connected in a series with-said secondary winding, and amagnetic core movable with'said secondary winding and having a portionmagnetically associated with said solenoid, a coupling between said coreand said solenoid varying in accordance with the spacing between saidwindings. I

6. In a constant current electrical apparatus, the combination of amagnetic core having a winding leg, of a plurality of windingssurrounding said leg, one of said windings being adapted to movelongitudinally along said leg in response to reaction between thecurrents flowing through said winding, and electromagnetic means forexerting a biasing force against said movable winding being a functionof the spacing between said windings, and means for varying the range ofsaid biasing force.

JUSTIN PETERSON.

